The prehistory of Western Sahara in a regional context: the archaeology of the "free zone"
by
Brooks, Nick
Tyndall Centre for Climate Change Research, Saharan Studies Programme and School of Environmental Sciences, University of East Anglia, Norwich, UK
Coauthors: Di Lernia, Savino ((Department of Scienze Storiche, Archeologiche, e Antropologiche dell’Antichità, Faculty of Human Sciences, University of Rome “La Sapienza”, Via Palestro 63, 00185 – Rome, Italy) and Drake, Nick (Department of Geography, King’s College, Strand, London WC2R 2LS).

The disputed territory of Western Sahara has long been inaccessible to research as a result of the military and political conflict between Morocco, which occupies some eighty per cent of the territory, and the Frente Polisario, the Algeria-based Western Saharan independence movement. This paper presents the findings of a two-week reconnaissance survey of the archaeology and environment of the Northern Sector of the Polisario-controlled zone of Western Sahara (Figure 1), which took place in September and October 2002, and comprised researchers from the UK and Italy. The results of the survey are described within the context of their relevance to the archaeology and environmental history of the wider Saharan region, after a consideration of the general environmental history of he Sahara as a whole. Fig. 1: Study area of the 2002 survey. The cultural history of the Sahara is intimately related to the existence of a succession of humid and arid episodes, which in turn are associated with periods of global warming and cooling respectively. Evidence from throughout the Sahara indicates that the region experienced a cool, dry and windy climate during the last glacial period, followed by a wetter climate with the onset of the current interglacial, with humid conditions being fully established by around 10,000 years BP, when we see the first evidence of a reoccupation of parts of the central Sahara by hunter gathers, most likely originating from sub-Saharan Africa (Cremaschi and Di Lernia, 1998; Goudie, 1992; Phillipson, 1993; Ritchie, 1994; Roberts, 1998). The cycle of glacial desiccation followed by interglacial greening is believed to be driven predominantly by variations in northern hemisphere insolation resulting from changes in the tilt of the Earth’s axis associated with the precessional cycle (Roberts, 1998). Stronger insolation leads to increase heating of the North African subcontinent, intensifying the African Monsoon, which penetrates deep into the Sahara. Superimposed on the interglacial humid episodes are brief periods of aridity lasting from decades to centuries, broadly coincident with cold events in the Atlantic that appear to be manifestations of internal climate variability that (Alley et al. 1997; Bond et al., 1997; Cremaschi et al., 2001, 2002; Di Lernia and Palombini, 2002). In the early Holocene, when northern hemisphere summer insolation was strong, these arid episodes were followed by recovery; however, the onset of aridity around 5000 years BP was followed by a long-term desiccation throughout the Sahara (Cremaschi, 1998; Jolly et al. 1998; Lioubimsteva 1995). While there is a high degree of homogeneity in the Saharan palaeoclimatic record on multi-millennial timescales (Jolly et al., 1998; Lézine, 1989; Petit-Maire et al., 1997), the timings of arid episodes and the onset of environmental desiccation are not identical at all locations (Alley et al., 1997; Gasse and van Campo, 1994; Goodfriend, 1991; Smith, 1998). This may be explained by a combination of geographical differences in the nature of the principal rain-bearing systems (particularly at the extremities of the Sahara), and the mediation of climate change impacts by local surface environments. The impacts of the final climatic desiccation of the Sahara on human populations would have been strongly mediated by the rapidity and nature of the corresponding environmental desiccation. Where surface water disappeared rapidly, human populations would have been forced to migrate to wetter areas; however, in certain areas populations undertook local adaptation to gradual desiccation by exploiting refugia in which water remained as a consequence of the near-surface geology or occasional rainfall resulting from local topography (Di Lernia et al., 2002; Mattingly et al., 2003). The area investigated during the 2002 field survey in Western Sahara is situated between the present day zones of westerly Atlantic rain-bearing systems to the northwest and monsoonal rainfall to the south, and is characterised by numerous ephemeral river channels. While further research is necessary to develop a detailed environmental chronology for the study area, two radiocarbon dates indicate wetter conditions in the region in the seventh millennium BP, with water present in one of the now-dry lakes in the fifth millennium BP (Brooks et al., 2003). These preliminary results are broadly consistent with data from the central Sahara indicating an early-middle Holocene humid episode followed by middle-late Holocene desiccation (Petit-Maire et al., 1997). Archaeological materials also indicate significant commonality with other Saharan regions. Acheulian and Aterian materials, and a single trihedral point, indicate that the study area was occupied in the Pleistocene, although the density of materials suggests that occupation may have been in the form of small, transient groups. The density of burial sites indicates a much larger population in the Holocene, and Holocene microlithic materials were also recorded. In particular, funerary monuments representing a wide range of typologies reflect the material culture of the central Sahara. Conical tumuli, platform burials and a V-type monument represent structures similar to those found in other Saharan regions and associated with human burials, appearing in sixth millennium BP onwards in northeast Niger and southwest Libya (Sivilli, 2002). In the latter area a shift in emphasis from faunal to human burials, complete by the early fifth millennium BP, has been interpreted by Di Lernia and Manzi (2002) as being associated with a changes in social organisation that occurred at a time of increasing aridity. While further research is required in order to place the funerary monuments of Western Sahara in their chronological context, we can postulate a similar process as a hypothesis to be tested, based on the high density of burial sites recorded in the 2002 survey. Fig. 2: Megaliths associated with tumulus burial (to right of frame), north of Tifariti (Fig. 1). A monument consisting of sixty five stelae was also of great interest; precise alignments north and east, a division of the area covered into separate units, and a deliberate scattering of quartzite inside the structure, are suggestive of an astronomical function associated with funerary rituals. Stelae are also associated with a number of burial sites, again suggesting dual funerary and astronomical functions (Figure 2). Further similarities with other Saharan regions are evident in the rock art recorded in the study area, although local stylistic developments are also apparent. Carvings of wild fauna at the site of Sluguilla resemble the Tazina style found in Algeria, Libya and Morocco (Pichler and Rodrigue, 2003), although examples of elephant and rhinoceros in a naturalistic style reminiscent of engravings from the central Sahara believed to date from the early Holocene are also present. The situation at Sluguilla is unusual in that carvings are located on isolated, largely horizontal limestone slabs exposed to the elements (Figure 3). Fig. 3: Example of engravings at Sluguilla, near the border with Algeria. The combination of familiar Saharan subjects and local stylistic innovation is also apparent at the previously recorded sites of Erqeiz and Irghayra (Soler et al, 1999) and the newly identified site of Bou Dheir (Brooks et al, 2003). These sites are all located along elevated areas overlooking wide plains, in contrast to Sluguilla, and are associated with paintings rather than carvings. Erqeiz and Bou Dheir are notable for their representations of large wild fauna, familiar from the central Sahara in the form of engravings (Dupuy, 1999, Jelínek, 2000; Phillipson, 1993). At Rekeiz an elephant and rhinoceros are depicted on the same vertical rock face in a location some distance from the main concentrations of paintings, while an elephant and a buffalo are recorded at Bou Dheir in close proximity to representations of human figures, hand prints, cattle, gazelle and a large painting that may be a wild or domesticated ovicaprid. Giraffe are represented in paintings at Bou Dheir and Rekeiz, and in engravings at Sluguilla, indicating that they occupied an important role in the lives of the prehistoric peoples of the region, as they did throughout the Sahara (Dupuy, 1999; van Hoek, 2003). Cattle feature prominently in the rock art of the Northern Sector, particularly at Erqueiz. They are also represented at Bou Dheir, in a particularly distinctive painted style. A remarkable isolated engraving of a cow with a smaller animal depicted inside the stomach, presumably an infant or unborn calf, was recorded on a rock at the edge of a plateau on which were located a number of funerary monuments, including platform and corbeille structures (Figure 4). Fig. 4: Representation of pregnant cow (?) in far north of study area (Wadi Tirnit). These images illustrate that cattle were crucial to the lives of the prehistoric peoples of Western Sahara, as they were throughout the Sahara (e.g. Di Lernia and Palombini, 2002; Holl and Dueppen, 1999). Ovicaprids are also a common theme in the rock paintings of the study area, although it is difficult to determine whether these images represent domestic or wild animals. At Rekeiz and Irghrayra sheep or goats are depicted in long lines consisting of many animals. The dominant painted panel at Bou Dheir is centred on a large image of an animal of uncertain type, possibly an ovicaprid or a wild herbivore, but clearly of great significance to the artist or artists (Figure 5). Human figures are represented only in the painted imagery recorded to date; they are absent from the recorded engravings of Sluguilla, although their presence at unrecorded sites cannot be discounted. Some of the figures at Bou Dheir are represented with distinctive crests or headdresses reminiscent of painted figures of Mediterranean or Near Eastern appearance in the central Sahara, while representations at Erqueiz are very different in appearance, suggesting at least two different population groups. Despite the large distances involved, it appears that the far west of the Sahara around the latitude of 25° N was far from isolated from the remainder of the greater Saharan region. The prehistoric inhabitants of Western Sahara hunted and recorded the same animals as their counterparts in central and eastern regions, and shared the same technologies. Fig. 5: Principal painted recess at the Bou Dheir rock shelter. As throughout the Sahara, they responded to the same pressures of climatic and environmental desiccation; the location of hearths within wide river channels suggests a congregation around diminishing water resources, while the depiction of a wide variety of more humid-climate fauna indicate Holocene desiccation following a humid phase. However, many questions remain regarding the chronology of human occupation and the processes of adaptation and cultural evolution. For example, was the region reoccupied at the same time as the recolonisation of the central Sahara, or did transient occupation continue through the arid period that preceded the Holocene? 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Date received: November 30, 2003

Copyright © 2003 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # camu-20.